Constraining hadronization mechanisms with $\rm \Lambda_{\rm c}^{+}$/D$^0$ production ratios in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV

The production of prompt $\rm \Lambda_{\rm c}^{+}$ baryons at midrapidity ($|y|<0.5$) was measured in central (0-10%) and mid-central (30-50%) Pb-Pb collisions at the center-of-mass energy per nucleon-nucleon pair $\sqrt{s_{\rm NN}} = 5.02$ TeV with the ALICE detector. The results are more precise, more differential in centrality, and reach much lower transverse momentum ($p_{\rm T}=1$ GeV/$c$) with respect to previous measurements performed by the ALICE, STAR, and CMS Collaborations in nucleus-nucleus collisions, allowing for an extrapolation down to $p_{\rm T}=0$. The $p_{\rm T}$-differential $\rm \Lambda_{\rm c}^{+}$/D$^0$ production ratio is enhanced with respect to the pp measurement for $4<p_{\rm T}<8$ GeV/$c$ by 3.7 standard deviations ($\sigma$), while the $p_{\rm T}$-integrated ratios are compatible within 1$\sigma$. The observed trend is similar to that observed in the strange sector for the $\Lambda/$K$^0_{\rm S}$ ratio. Model calculations including coalescence or statistical hadronization for charm-hadron formation are compared with the data.

Λ + c production in Pb-Pb collisions at √ s NN = 5.02 TeV ALICE Collaboration 0.8, at least 50 clusters in the TPC available for particle identification (PID), and a χ 2 /ndf < 1.25 in the TPC (where ndf is the number of degrees of freedom involved in the track fit procedure) were considered for the analysis.Moreover, a minimum number of two hits (out of six) in the ITS, with at least one in the inner two layers, were required for the proton track.The selection of tracks with |η| < 0.8 limits the Λ + c acceptance in rapidity.For this reason a fiducial acceptance selection was applied on the rapidity of the Λ + c candidates, |y lab | < y fid (p T ), where y fid increases from 0.6 to 0.8 in 1 < p T < 5 GeV/c, and y fid = 0.8 for p T > 5 GeV/c.Unlike the previous analysis based on linear selections [33], the Λ + c -candidate selection was performed using multivariate techniques based on the Boosted Decision Tree (BDT) algorithm provided by the XGBoost package [51].Before the training, loose kinematic and topological selections were applied to the K 0 S -meson candidate together with the particle identification of the proton-candidate track.The PID was performed using the specific ionization energy loss dE/dx in the TPC gas and the time of flight from the interaction point to the Time-Of-Flight (TOF) detector [52,53].The BDT training was performed considering as signal candidates prompt (not coming from beauty-hadron decays) Λ + c decays from MC simulations.Background candidates were taken from the sidebands of the invariant mass distribution in data (defined to be outside a 80 MeV/c 2 window around the Λ + c mass value reported by the PDG [28]).The variables that were most important in the training were the PID-related variables of the protoncandidate track, the displacement of the proton-candidate track from the primary vertex, the distance between the K 0 S -meson decay vertex and the primary vertex, and the cosine of the pointing angle between the K 0 S -meson candidate line of flight and its reconstructed momentum vector.Independent BDTs were trained for the different p T and centrality intervals.
The selection on the BDT output was tuned in each p T interval to maximize the expected statistical significance, which is estimated using i) the expected signal obtained from FONLL calculations [54,55] scaled by the corresponding T AA [45] and multiplied by the BDT selection efficiency and ii) the expected background estimated from an invariant mass sideband fit using a fraction of the data.
After applying selections on the BDT output, the yields of Λ + c baryons were extracted in each p T interval via binned maximum-likelihood fits to the candidate invariant mass distributions.The fitting function consisted of a Gaussian term to estimate the signal and a second-, third-, or fourth-order polynomial function (depending on the p T interval) to estimate the background.The default background fitting function was chosen after dedicated studies to obtain a good description of the invariant mass distribution in the sidebands.The other functions were considered for evaluating the systematic uncertainty.
The raw-yield extraction is challenging, especially at low p T with signal-to-background ratios below one per mille and relative statistical uncertainties on the extracted raw yield varying between 15-35%, as presented in Appendix A. Given the critical signal extraction due to the low signal-to-background ratios, the width of the Gaussian term for the signal was fixed to the value obtained from simulations.It was verified that the widths from the simulation were consistent within uncertainties to those extracted from fits to data without constraints on the width of the Gaussian (with a relative uncertainty of 1-2% in simulation and 20-30% in data).In addition, the stability of the signal extraction was further verified by i) fitting purely background candidates from simulations and ii) by repeating the fit after subtracting a background component estimated with an event-mixing technique.For the latter, the events were grouped in pools based on the primary-vertex position along z and the estimated centrality.For the first study, none of the invariant mass fits allowed to extract a signal in the Λ + c invariant mass region.For the second study, fits to the background-subtracted invariant mass distributions resulted in compatible Λ + c raw yields to the ones extracted from the default fits.
The corrected yields of prompt Λ + c baryons were obtained in each centrality interval as The raw yield values N Λ ± c raw , extracted in a given p T interval of width ∆p T , were divided by a factor two and multiplied by the prompt fraction f prompt to obtain the charge-averaged yields of prompt Λ + c .Furthermore, they were divided by c ∆y × (A × ε), enclosing the rapidity coverage and the acceptancetimes-efficiency, by the BR of the decay channel, and by the number of analyzed events N ev .
The (A × ε) correction was determined from MC simulations, using samples not employed in the BDT training.The generated p T spectrum used to calculate the efficiencies was reweighted to reproduce the shape obtained from the D 0 measurement [56] multiplied by Λ + c /D 0 calculations from the TAMU model [8] in 0-10% and 30-50% Pb-Pb collisions at √ s NN = 5.02 TeV.The (A × ε) increases from 1% (3%) at low p T to about 12% (16%) at high p T for central (mid-central) collisions.The correction factor for the rapidity acceptance, c ∆y , was computed as the ratio between the generated Λ + c -baryon yield in ∆y = 2y fid (p T ) and that in |y| < 0.5 using the reweighted p T shape and the rapidity distribution from PYTHIA 8 simulations [23].It was verified in [56] that for D mesons the calculation of c ∆y is only weakly sensitive to the rapidity distribution used for its calculation.
The f prompt fraction of the reconstructed signal was estimated using a similar strategy as described in [33].In particular, the beauty-hadron production cross section was estimated with FONLL calculations [54,55], the fraction of beauty quarks that fragment into Λ 0 b was estimated from the Λ 0 b /(B 0 + B + ) ratio measured by LHCb in pp collisions at √ s = 13 TeV [57] following the same strategy as used in [11], and the kinematics of the decay of beauty hadrons H b → Λ + c + X simulated with PYTHIA 8 [23].The branching ratios were taken as implemented in PYTHIA 8.243, corresponding to approximately 82% for Λ 0 b baryons and 2% for either B 0 , B + , and B + s mesons.In addition, the f prompt fraction is modified to account for the nuclear modification factor of Λ + c baryons from beauty-hadron decays.The central correction is chosen such that R non-prompt AA = 2 × R prompt AA as predicted by the "Catania" theoretical calculation [6].The resulting f prompt fraction was found to be about 0.97 at low p T and about 0.81 at high p T .
The systematic uncertainties of the Λ + c corrected yields include contributions from i) the extraction of the raw yield, ii) the tracking efficiency, iii) the Λ + c selection efficiency, iv) the MC generated p T spectra, v) the statistical uncertainty of the efficiency, and vi) the subtraction of feed-down Λ + c baryons from bhadron decays.The estimated values of these systematic uncertainties are summarized for representative p T intervals in Table 1.In addition, a global systematic uncertainty due to the centrality interval definition (2% for mid-central, negligible for central) [56] and the branching ratio (5.5%) [28] was assigned.For the R AA observable, the uncertainty of the pp cross section normalization uncertainty (2.1%) [11] and of the average nuclear overlap function (0.7% for central, 1.6% for mid-central) [45] are included in the global normalization uncertainty.
The systematic uncertainty of the raw-yield extraction was estimated by repeating the invariant mass fits varying the lower and upper limits of the fit range, the functional form of the background fit function, and considering the Gaussian width (mean) as a free (fixed) parameter in the fit.In order to test the sensitivity to the line shape of the signal, a bin-counting method was used, in which the signal yield was obtained by integrating the invariant-mass distribution after subtracting the background estimated from the sideband fit, as well as by studying the signal shape in the MC simulations using multiple stacked Gaussian functions rather than a single one.The procedure to estimate the systematic uncertainty of the track-reconstruction efficiency includes variations of the track-quality selection criteria for all decay tracks and studies on the probability to match TPC tracks to the ITS clusters in data and simulation for the proton-candidate track.The latter comparison was performed after weighting the relative abundances of primary and secondary particles in simulation to those in data [33].The systematic uncertainty of the Λ + c selection efficiency was estimated by repeating the analysis with different selections on the BDT output, resulting in up to 50% lower and 20-50% higher efficiency values.Possible systematic effects due to the loose PID selection, applied prior to the BDT one, were investigated by comparing the PID-selection efficiencies in data and in simulations and found to be negligible.Both the tracking-and PID-efficiency studies were performed using pure samples of pions (from K 0 S decays) and protons (from Λ decays).An additional contribution derives from the p T spectra of Λ + c generated in the simulation, which was estimated by using the Λ + c /D 0 predictions of the Catania model [7] and the SHMc [10] instead of the TAMU prediction [8] in the p T -shape reweighting procedure, as well as by an iterative method using a parametrization of the measured p T -differential production yields.Finally, the systematic uncertainty of the feed-down subtraction was estimated by varying the FONLL parameters as prescribed in [55] and the function describing the Λ 0 b fragmentation fraction within the quoted experimental uncertainty as reported in [11], as well as by varying the hypothesis on R non-prompt AA .For the latter, an interval 1/3 < R non-prompt AA /R prompt AA < 3 was considered, wider with respect to that used for non-strange D mesons [56] to cover possible yet unmeasured differences between the modification of charm-and beauty-baryon production in Pb-Pb collisions with respect to the one in pp collisions.
The sources of systematic uncertainty considered in this analysis are assumed to be uncorrelated among each other and the total systematic uncertainty in each p T and centrality interval is calculated as the quadratic sum of the individual uncertainties.For the Λ + c /D 0 ratio, the Λ + c and D 0 uncertainties were considered as uncorrelated except for the tracking efficiency and the feed-down contribution, which are assumed correlated and thus partially cancel in the ratio, and the systematic uncertainty of the centrality interval definition, which fully cancels.For the R AA , the pp and Pb-Pb uncertainties were considered as uncorrelated except for the branching ratio uncertainty and the feed-down contribution, which both partially cancel out (the former because the pp measurement considers additional decay modes).Finally, in case of the p T -integrated Λ + c /D 0 ratio, there is a correlation between the extrapolation uncertainty of the Λ + c baryon and the measured uncertainties of the Λ + c and D 0 hadrons.To treat this correlation, the extrapolation uncertainty is divided into a correlated part (estimated as the extrapolation uncertainty when considering only the shape predicted by TAMU) and an uncorrelated part (the total extrapolation uncertainty subtracting the correlated part) with respect to the measured uncertainties.The uncorrelated part is summed in quadrature with the measured uncertainties, while the correlated part is added linearly.

Results
The p T -differential production yields of prompt Λ + c baryons are shown in Fig. 1 (left panel).The statistical and total systematic uncertainties are shown as uncertainty bars and boxes, respectively, for all figures.The results are compared with the pp reference cross section [11] multiplied by the corresponding T AA [45], i.e. the denominator of the R AA observable that is discussed later.In the right panel of Fig. 1, the ratio of the production yields of Λ + c baryons to that of D 0 mesons, measured in the same centrality intervals [56], are presented together with the pp measurement at the same collision energy [11].The ratios increase from pp to mid-central and central Pb-Pb collisions for 4 < p T < 8 GeV/c with a significance of 2.0 and 3.7 standard deviations, respectively.This trend is qualitatively similar to what is observed for the p/π [58] and Λ/K 0 S [59] ratios, which both show a distinct peak at intermediate p T that increases in magnitude (by about a factor 2 for mid-central and a factor 3 for central Pb-Pb collisions with respect to minimum-bias pp collisions) and shifts to higher p T values (from about 2 GeV/c in pp to 4 GeV/c in central Pb-Pb collisions) with increasing multiplicity.The central and mid-central Λ + c /D 0 ratios in 12 < p T < 24 GeV/c are compatible with the measurement by CMS in 0-100% Pb-Pb collisions in p T > 10 GeV/c region [15].The central Λ + c /D 0 ratio in 6 < p T < 8 GeV/c is in agreement with the previous measurement of ALICE in the 0-80% centrality interval [33].For p T > 4 GeV/c, the ratio measured in central collisions resembles in magnitude and p T trend the one reported by STAR in 2.5 < p T < 8 GeV/c in 10-80% Au-Au collisions at √ s NN = 200 GeV [34].Note that the large centrality classes of the previous measurements are dominated by the production in the most central events (given the scaling of the Λ + c yields with N coll × R AA ), hence they are compared to the measurement in 0-10%.The nuclear modification factor R AA of prompt Λ + c is compared with the R AA of prompt D + s mesons [60] and the average R AA of prompt D 0 , D + , and D * + mesons [56] in Fig. 2  The suppression of all charm-meson (baryon) species from p T 3 (6) GeV/c is understood as being primarily due to the interaction of charm quarks with the quark-gluon plasma, which modifies their momentum spectra, as discussed extensively for the non-strange D mesons in [56].In central collisions in the region 4 < p T < 8 GeV/c, there is a hint of a hierarchy In mid-central collisions, this hierarchy is less pronounced.In the p T 10 GeV/c region, where the hadronization is expected to occur mainly via fragmentation, the R AA of the various charm-hadron species are compatible within uncertainties.[30,31] are also compared with the existing measurement in pp collisions [11].The Catania model [7,30] assumes that a QGP is formed in both pp and Pb-Pb collisions.In Pb-Pb collisions heavy-quark transport is implemented via the Boltzmann equation, and in both pp and Pb-Pb collisions hadronization occurs either via coalescence, implemented through the Wigner formalism, or via fragmentation in case the quarks do not undergo coalescence.The TAMU model [8] describes charm-quark transport in an expanding medium with the Langevin equation and hadronization proceeds primarily via coalescence, implemented with a Resonance Recombination Model (RRM) [62].Left-over charm quarks not undergoing coalescence are hadronized via fragmentation.In pp collisions, the charm-hadron abundances are instead determined with a statistical hadronization approach [31].In both collision systems the underlying charm-baryon spectrum includes unobserved excited states [28] predicted by the Relativistic Quark Model (RQM) [63] and lattice QCD [31].Finally, for the SHMc predictions [10], which include only charm mesons and baryons established experimentally, the charmhadron p T spectra are modeled within a core-corona approach.The core contribution represents the central region of the colliding nuclei where charm quarks achieve local thermal equilibrium in a hydrodynamically expanding QGP.The charm-hadron spectra in the corona contribution are, instead, parameterized from measurements in pp collisions.The p T -spectra modification due to resonance decays is computed using the FastReso package [64].The theoretical uncertainty bands shown in Fig. 3 derive from: an assumed range of branching ratios (50-100%) for the decays of the RQM-augmented excited states into Λ + c for the TAMU model; the variation of about 10% of the Wigner function widths in the Catania calculations; and mainly the uncertainties on the pp spectra fits in the SHMc predictions at high p T .The SHMc describes the Λ + c /D 0 ratio in mid-central collisions, but underpredicts the ratio in 4 < p T < 8 GeV/c in central collisions by about 2.5σ of the combined statistical, systematic, and theoretical uncertainties.The prediction of the Catania model in central collisions underestimates the Λ + c /D 0 ratio at intermediate p T , although the deviation is at maximum 2.5σ .The TAMU predictions reproduce the magnitude and shape of the Λ + c /D 0 ratios.While both these fragmentation plus coalescence model calculations are able to describe the Λ + c /D 0 ratio in Au-Au collisions at √ s NN = 200 GeV in the 10-80% centrality interval [34], the TAMU model better reproduces the data in central Pb-Pb collisions.A pure coalescence scenario from an older version of the Catania model was reproducing better the previous ALICE measurement in 0-80% Pb-Pb collisions [33].The Catania and TAMU predictions also describe both the magnitude and p T shape of the measured Λ + c /D 0 ratio in pp collisions.Instead, at forward rapidity, the TAMU model predicts a systematically higher Λ + c /D 0 ratio than measured by LHCb in 65-90% Pb-Pb collisions at √ s NN = 5.02 TeV [39].
The Λ + c production yield for p T > 0 was estimated by summing up the measured p T -differential yields and the extrapolated Λ + c yield for p T < 1 GeV/c.The Λ + c yield in 0 < p T < 1 GeV/c was obtained as the product of the Λ + c /D 0 ratio value estimated by interpolating the ratio in the measured p T interval with model expectations and the measured D 0 yield [56].The interpolation procedure was performed using the shape predicted by TAMU [8], Catania [7] (not available for 30-50%), SHMc [10], and blast-wave [65] calculations, leaving the normalization as a free parameter.The shape from TAMU was chosen as the central value based on the χ 2 /ndf values, while the difference between the obtained yields was con- sidered in the systematic uncertainty due to the extrapolation.The results for the prompt Λ + c production yields per unit of rapidity in |y| < 0.5 are dN/dy = 3.27± 0.42 (stat)± 0.45 (syst)± 0.16 (BR) +0.46  −0.29 (extr) for central collisions and dN/dy = 0.70 ± 0.09 (stat) ± 0.09 (syst) ± 0.04 (BR) +0.07 −0.05 (extr) for mid-central collisions, where the visible yield is about 81% of the total for both centrality classes.The SHMc [10] predicts lower values, dN/dy = 1.55 ± 0.23 and dN/dy = 0.316 ± 0.036, respectively.
The measured Λ + c /D 0 ratios, obtained dividing the p T -integrated Λ + c and D 0 yields [56], are presented in Fig. 4, taking into account the correlation between the measured and extrapolated uncertainties.Similarly to what is observed for the Λ/K 0 S ratio [59, 66], the Λ + c /D 0 ratios in Pb-Pb collisions are compatible with the p T -integrated Λ + c /D 0 ratios at pp and p-Pb multiplicities [11,32] within one standard deviation of the combined uncertainties.This observation, together with the significant enhancement of the Λ + c /D 0 ratio at intermediate p T with increasing multiplicity, seen here and in pp collisions [32], suggests a modified (and perhaps similar) mechanism of hadronization in all hadronic collision systems with respect to charm fragmentation tuned on e + e − and e − p measurements (PYTHIA 8 point in Fig. 4).The coalescence models of [4,5,9], in which the Λ + c /D 0 ratio depends on the balance of quark and diquark densities at hadronization time, expect a dependence of the p T -integrated Λ + c /D 0 ratio on multiplicity (leading to an increase by about a factor 3-10 in nuclear collisions compared with their pp baseline), which is not observed.The measured p T -differential enhancement may, instead, predominantly be caused by altered production ratios for baryons and mesons following from the phase-space distribution of the quarks.This can arise from the collective radial expansion of the system, for which, in the coalescence picture (Catania and TAMU Pb-Pb points in Fig. 4), the accounting of space-momentum correlations in the procedure have been observed to be fundamental in [8,9].Interactions in the hadronic phase are, on the contrary, expected to have a small effect on the Λ + c /D 0 ratio [6,67].The statistical hadronization approach (SHMc and TAMU pp points in Fig. 4), can also describe both the p T -differential and p T -integrated observations with the, currently debated, caveat that for the proper normalization yet unobserved charm-baryon states need to be assumed [10,31].Note that the authors of the TAMU model include these additional states already in their predictions, while for the SHMc model it is not the baseline.The uncertainty of the p T -integrated yield in Pb-Pb collisions is still relatively large, and more precise measurements at low p T will help to further discriminate between charm-baryon formation scenarios.Finally, Fig. 5 shows the R AA of prompt Λ + c baryons compared with the previously introduced theoretical models [7, 8, 10].The Catania R AA predictions are from an earlier version of the model than the Λ + c /D 0 predictions and they do not have an uncertainty band.The TAMU model provides a good description of the R AA , over the whole p T range, in both central and mid-central collisions.The Catania model describes the data in both central and mid-central collisions for p T > 2 GeV/c, however for p T < 2 GeV/c the model predicts a R AA higher than unity which is disfavored by data.Both these models do not include charm-quark interactions with medium constituents via radiative processes, hence are not expected to describe the R AA for p T > 8 GeV/c.The SHMc model instead significantly underestimates the Λ + c R AA over the whole p T range.

Conclusions
In summary, the measurements of the production yield of prompt Λ c /D 0 ratios increase from pp to central Pb-Pb collisions for 4 < p T < 8 GeV/c with a significance of 3.7 standard deviations, while the p T -integrated ratios are compatible within one standard deviation.Both observations are in qualitative agreement with the baryon-to-meson ratio for strange hadrons.The measurements are described by theoretical calculations that include both coalescence and fragmentation processes when describing the hadronization of heavy flavors in the QGP.The upgraded ALICE detector for the LHC Runs 3 and 4 will increase its acquisition rate by up to a factor of about 50 in Pb-Pb collisions and the tracking precision by a factor 3-6, meaning future measurements of Λ + cbaryon production will allow for stronger constraints on the heavy-quark hadronization mechanisms in heavy-ion collisions [68].

Figure 1 :
Figure 1: Left: p T -differential production yields of prompt Λ + c in central (0-10%) and mid-central (30-50%) Pb-Pb collisions at √ s NN = 5.02 TeV compared to the pp reference [11] scaled by the T AA of the corresponding centrality interval [45].Right: Λ + c /D 0 ratio in central and mid-central Pb-Pb collisions at √ s NN = 5.02 TeV compared with the results obtained from pp collisions [11].

Figure 2 :
Figure 2: Nuclear modification factor R AA of prompt Λ + c baryons in central (0-10%; left) and mid-central (30-50%; right) Pb-Pb collisions at √ s NN = 5.02 TeV, compared with the R AA of prompt D + s [60] and the average of prompt non-strange D mesons [56].The normalization uncertainties are shown as boxes around unity.

Figure 3
Figure 3 compares the p T -differential Λ +c /D 0 ratios with different theoretical predictions: Catania [7], TAMU[8], and the GSI-Heidelberg statistical hadronization model (SHMc)[10].The predictions of Catania and TAMU for pp collisions[30,31] are also compared with the existing measurement in pp collisions[11].The Catania model[7,30] assumes that a QGP is formed in both pp and Pb-Pb collisions.In Pb-Pb collisions heavy-quark transport is implemented via the Boltzmann equation, and in both pp and Pb-Pb collisions hadronization occurs either via coalescence, implemented through the Wigner formalism, or via fragmentation in case the quarks do not undergo coalescence.The TAMU model [8] describes charm-quark transport in an expanding medium with the Langevin equation and hadronization proceeds primarily via coalescence, implemented with a Resonance Recombination Model (RRM)[62].Left-over charm quarks not undergoing coalescence are hadronized via fragmentation.In pp collisions, the charm-hadron abundances are instead determined with a statistical hadronization approach[31].In both collision systems the underlying charm-baryon spectrum includes unobserved excited states[28] predicted by the Relativistic Quark Model (RQM)[63] and lattice QCD[31].Finally, for the SHMc predictions [10], which include only charm mesons and baryons established experimentally, the charmhadron p T spectra are modeled within a core-corona approach.The core contribution represents the central region of the colliding nuclei where charm quarks achieve local thermal equilibrium in a hydrodynamically expanding QGP.The charm-hadron spectra in the corona contribution are, instead, parameterized from measurements in pp collisions.The p T -spectra modification due to resonance decays is computed using the FastReso package[64].The theoretical uncertainty bands shown in Fig.3derive from: an assumed range of branching ratios (50-100%) for the decays of the RQM-augmented excited states into Λ + c for the TAMU model; the variation of about 10% of the Wigner function widths in the Catania calculations; and mainly the uncertainties on the pp spectra fits in the SHMc predictions at high p T .

Figure 5 :
Figure 5: Nuclear modification factor R AA of prompt Λ + c baryons in central (0-10%; left) and mid-central (30-50%; right) Pb-Pb collisions at √ s NN = 5.02 TeV, compared with model predictions.When estimated, the model uncertainty is shown as a shaded band.

Figure A. 1 :
Figure A.1: Invariant mass (M) distributions of Λ + c → pK 0 S → pπ + π − candidates and charge conjugates in different p T intervals in central (0-10%; top) and mid-central (30-50%; bottom) Pb-Pb collisions at √ s NN = 5.02 TeV.The blue solid lines show the total fit functions and the red dashed lines are the combinatorial-background terms.The values of the mean (µ) and the width (σ ) of the signal peak are reported together with the signal counts (S) and the signal-over-background ratio (S/B) in the mass interval (µ − 3σ , µ + 3σ ).
Λ + c production in Pb-Pb collisions at √ s NN = 5.02 TeV ALICE Collaboration B The ALICE Collaboration Λ + c production in Pb-Pb collisions at √ s NN = 5.02 TeV

Table 1 :
Relative systematic uncertainties of the prompt Λ + c -baryon corrected yield in Pb-Pb collisions for central and mid-central events in representative p T intervals.